Device for reliably determining biometric measurement variables of the whole eye

ABSTRACT

A device for determining biometric variables of the eye, as are incorporated in the calculation of intraocular lenses including a multi-point keratometer and an OCT arrangement. The keratometer measurement points are illuminated telecentrically and detected telecentrically and the OCT arrangement is designed as a laterally scanning swept-source system with a detection region detecting the whole eye over the whole axial length thereof. The multi-point keratometer ensures that a sufficient number of keratometer points are available for measuring the corneal surface. By contrast, telecentricity ensures that the positioning inadequacies of the measuring instrument in relation to the eye to be measured do not lead to a local mismatch of the reflection points. The swept-source OCT scan detects the whole eye over the length thereof so that both anterior chamber structures and retina structures can be detected and a consistent whole eye image can be realized.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 16/913,308,filed Jun. 26, 2020, entitled, “Device for Reliably DeterminingBiometric Measurement Variables of the Whole Eye”, which is acontinuation of application Ser. No. 15/583,439, filed May 1, 2017,entitled “Device for Reliably Determining Biometric MeasurementVariables of the Whole Eye”, which is a continuation of application Ser.No. 14/431,450, filed Mar. 26, 2015, entitled “Device for ReliablyDetermining Biometric Measurement Variables of the Whole Eye”, now U.S.Pat. No. 9,649,027 issued May 16, 2017, which is a national stage entrypriority of PCT Application No. PCT/EP2013/070199, filed Sep. 27, 2013,which claims priority to German Patent Application No. 10 2012 019474.9, filed Sep. 28, 2012, and also claims priority to U.S. ProvisionalApplication No. 61/707,004, filed Sep. 28, 2012, each of which is herebyfully incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a device for determining biometricvariables of the eye, as are incorporated in the calculation ofintraocular lenses. Such variables are the radii—including theorientation thereof—of the corneal front side and the corneal rear side,asphericity of the cornea, thickness of the cornea—in the center or elseas one- or two-dimensional profile —, anterior chamber depth, lensthickness, radii of the lens front side and/or rear side, axis length ofthe eye, in general the position and shape of the optically effectiveinterfaces or the areas relevant optically to the visual faculty of theeye such as corneal front/rear sides, lens front side and rear side,retina in the eye. These variables or some of these variables arerequired for calculating intraocular lenses—referred to below as IOLcalculation—in accordance with known IOL equations or by means of raytracing methods.

BACKGROUND

The prior art has only disclosed OCT (optical coherence tomography)systems and topography/OCT combined systems for measuring the biometricvariables of the whole eye. Although Scheimpflug, PCI (partial coherenceinterference) and topography systems or combined instruments of samemeasure some of the aforementioned variables, these combinations cannotmeasure all parameters of the eye. In particular, it is not possible tomeasure the lens rear side and the retina, or the respective profile ofthese areas, since these systems, even in a combined system, arerestricted to measuring the anterior chamber and the axialone-dimensional length of the eye.

Only OCT systems with anterior and posterior chamber measurements of theeye and topography/OCT systems, likewise with posterior and anteriorchamber measurement, are able to measure the whole eye.

A further possible combination is a combination oftopography/Scheimpflug system for the anterior chamber measurement andan OCT system for the posterior chamber measurement. However, since theOCT can also detect the anterior chamber, the gain from the Scheimpfluganterior chamber measurement is low compared to the additional costs.

Compared to the topography/OCT combined systems, pure OCT systems aredisadvantageous in that measuring the topography of the cornea by meansof conventional topometers (in particular Placido systems) issubstantially more accurate than the measurements of the OCT systemswhich are influenced by movement artifacts. Although said OCT systemscan reduce these movement artifacts by faster measurements or bymeasurements which are registered to the eye, this is only possible withsignificant outlay and not readily possible in a reliable enough manner.

By way of example, a combination of Placido topographs and time domainB-scan OCT is described as topography/OCT combined system inUS2004/066489. In principle, this allows the whole eye to be measuredbiometrically. However, the described device exhibits some significantdisadvantages, which reduce the reliability of the measurement values.

Although Placido topography has a very high resolution, it is lessreproducible in terms of reconstructing the surface when compared tokeratometer measurements. This is due, firstly, to the assumptions madeduring the reconstruction of the topography in order to achieve the highresolution and/or in the lacking telecentricity/insufficientfocusability of many topography systems compared to keratometers, and sopositioning errors of the measurement instrument in relation to thepatient become relevant during the topography measurement.

Furthermore, Placido topographs do not allow so-called Skrew rays to betaken into account, which are always generated in the case of thePlacido ring illumination when the cornea is curved not only in acentral plane through the corneal vertex but also in a planeperpendicular thereto, i.e. if it has azimuthal curvature. As a resultof not taking this into account, the corneal surface is not reproducedcorrectly. Thus, overall, a Placido topograph does not reproduce theradius or, in general, the front side of the cornea reliably enough asrequired for the IOL calculation.

Furthermore, time-domain OCT systems are too slow and competitivelypriced spectrometer-based systems do not have the axial resolutionand/or have a too small axial scanning or detection depth such that theeye length does not occur with the resolution required for the IOLcalculation or such that there are only partial depth measurements.However, whole-eye biometrics, i.e. establishing the areas of the wholeeye optically relevant to the visual faculty of the eye in terms oftheir position and their profile in the eye, are, in principle, possiblein both cases by separate measurement of the anterior and posteriorchamber and subsequent synthesis of the data, but the registration ofthe images to one another is often unreliable due to lack of a suitablecommon reference variable in the segment images.

Therefore, the Placido time-domain OCT system does not allow allbiometric data to be obtained in a sufficiently reliable and simplemanner for the IOL calculation.

A combination of a simple keratometer and a B-scan OCT is described as atopography/OCT combined system in US20050203422. This system also allowsimportant biometric variables of the biometrics of the eye to bedetermined. However, the described device also exhibits some significantdisadvantages, which reduce the reliability of the measurement values orleaves open important points which are relevant to whole-eye biometrics:

The described keratometer merely allows the robust measurement of theradii on the front side of the cornea. A higher-order description of thecorneal surface or a description with a higher resolution than that ofthe described keratometer is not possible. However, this is increasinglyrequired for the calculation of intraocular lenses (abbreviated IOLs),in particular for toric IOLs.

Furthermore, this does not solve the problem of assigning the topographymeasured by the keratometer to the spatial data from the OCT data, nordoes it ensure that the OCT measurements are taken particularly quicklyin order to compensate for the eye movement during the measurement.

SUMMARY

The present invention is based on the object of disclosing a devicewhich measures measurement values for the biometric variables at the eyein a quick, reliable and reproducible fashion and with the requiredaccuracy and resolution, which biometric variables are relevant to thecalculation of intraocular lenses, also to those calculations whichassume whole-eye biometrics.

In particular, the areas of the whole eye which are optically relevantto the visual faculty of the eye should be determined in terms of theirposition and their profile in the eye, which is referred to as whole-eyebiometrics below. Here, the aforementioned variables are in theforeground, but it is also possible to use the device to extractdifferent variables of the eye, which have not been used up until now,from the measurement data, in particular also those variables which arerequired for simulating an optical model of the eye.

The device for measuring biometric variables of the eyes for calculatingintraocular lenses, consisting of a multi-point keratometer and an OCTarrangement, achieves this object by virtue of the fact that themulti-point keratometer is configured such that the keratometermeasurement points are illuminated telemetrically and detectedtelecentrically and that the OCT arrangement is designed as a laterallyscanning swept-source system with a detection region detecting the wholeeye over the whole axial length thereof.

The multi-point keratometer ensures that, firstly, a sufficient numberof keratometer points are available for measuring the corneal surfacewith a high resolution, but that the density of the measurement pointsis low enough for it to be possible to detect the Skrew rays. Bycontrast, the telecentricity ensures that the positioning inadequaciesof the measurement instrument in relation to the eye to be measured donot lead to a local mismatch of the reflection points.

What the swept-source OCT scan, which captures the whole eye over thelength thereof, achieves is that both anterior chamber and retinastructures can be detected in the A-scan or B-scan and hence anorientation on the basis of the retina and the anterior chamber/corneabecomes possible during the scan. This makes it easier to combine the A-and/or B-scans to form a consistent whole-eye image. Here, theswept-source OCT is better than other OCT variants, such as time domainOCTs or spectrometer-based OCTs, in ensuring fast, movementartifact-free measurement of the A-scan over the whole eye length.

The above summary is not intended to describe each illustratedembodiment or every implementation of the subject matter hereof. Thefigures and the detailed description that follow more particularlyexemplify various embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

Subject matter hereof may be more completely understood in considerationof the following detailed description of various embodiments inconnection with the accompanying figures, in which:

FIG. 1 depicts a basic optical design of an example embodiment thedevice.

FIGS. 2 a and 2 b depict two B-scans, which are recorded in differentOCT measurement modes: in an anterior chamber mode and in a retina moderespectively.

FIG. 3 depicts an example embodiment of the B-scan/keratometer geometryof the device.

FIG. 4 illustrates the effect of Skrew rays when measuring thetopography and in the case of OCT measurements.

FIGS. 5 a and 5 b depict two embodiments of the basic design of anexample swept-source OCT measurement system.

While various embodiments are amenable to various modifications andalternative forms, specifics thereof have been shown by way of examplein the drawings and will be described in detail. It should beunderstood, however, that the intention is not to limit the claimedinventions to the particular embodiments described. On the contrary, theintention is to cover all modifications, equivalents, and alternativesfalling within the spirit and scope of the subject matter as defined bythe claims.

DETAILED DESCRIPTION OF THE DRAWINGS

The device according to the invention for measuring biometric variablesof the eye for calculating intraocular lenses consists of a multi-pointkeratometer and an OCT arrangement, wherein the multi-point keratometeris configured such that the keratometer measurement points areilluminated telecentrically and detected telecentrically and that theOCT arrangement is designed as a laterally scanning swept-source systemwith a detection region detecting the whole eye over the whole axiallength thereof.

FIG. 1 shows a basic optical design of the device: by means of the beamsplitter 3, an OCT system 2 is unified with a multi-point keratometersystem 1 on a common instrument axis 28 such that both can biometricallymeasure the eye 27 in a laterally assignable manner.

Here, the multi-point keratometer system 1 consists of several lightsources, preferably LEDs 4, at different radial distances from theinstrument axis 28. Lens attachments 29 ensure that the LEDstelecentrically illuminate the cornea in punctiform fashion by collinearbeams. The beams reflected by the cornea are detected by a camera 5,upstream of which a telecentricity aperture 6 has been attached.

Instead of individual LEDs with an attachment lens, collimated lightbeams can alternatively be produced by appropriately designed Fresnellenses, so-called fraxicons, using one or a few LEDs. This isparticularly advantageous if very many mutually spaced apart collimatedlight beams are intended to be produced.

The telecentric design of the illumination and of the detection reducesthe sensitivity with respect to positioning errors. This is because as aresult of the telecentricity, only rays whose angle in relation to thecornea is known and which are independent of distance contribute tobuilding up the image. Therefore this design ensures a higherreproducibility of the measurement of variables such as the cornealradius than in the case of a Placido topograph topographer and hence thedesign is more reliable for obtaining IOL determination relevantparameters than a Placido topographer.

In a first embodiment, the keratometer illuminates and measures an anglecorresponding to that of the keratometer of the IOLMaster by Carl ZeissMeditec AG at 6 measurement points, which are arranged on a ring aroundthe instrument axis, in particular at an illumination angle of between17 and 18 degrees with respect to the instrument axis. This ensures thateffects due to different angular alignments do not have to be taken intoaccount when comparing measurement data from the IOLMaster and from thedevice according to the invention.

In a further embodiment, the keratometer illuminates and measures atseveral points which are distributed on several rings around theinstrument axis. Here, at least 12 points which are arrangedsymmetrically around the instrument axis on at least 2 rings arepreferred.

Here, an arrangement with 3 rings with 6 points each is particularlypreferred. To this end, FIG. 3 shows a possible arrangement. What the 3ring arrangement ensures is that essential variables of the descriptionof a corneal surface are measured, which variables are expedient for theIOL calculation of current IOLs to a good approximation: corneal radius,astigmatism or the 2 main radii and the position of the axis for one ofthe radii, corneal asphericity. What the rotation of the points of thefirst and the third rings in relation to the position of the points ofthe second ring, as shown in FIG. 3 , achieves in particular is that themeasurement points lie in regions at which a Zernike description of thecorneal surface at a low order would expect the largest deviationscompared to a spherical surface for many eyes. Furthermore, a geometrylike in the IOLMaster keratometer can also be provided for thekeratometer illumination of one of the rings in this case.

Here, the scanning direction of the OCT arrangement is preferablyaligned in such a way that at least one B-scan of the OCT runs throughat least one keratometer measurement point.

In order to supply an even higher resolution for a refined resolution ofthe corneal surface or for the more precise diagnosis of eye disorders,the keratometer illuminates and measures at more than 30 but less than4000 keratometer measurement points, wherein the keratometer points aredistributed on several rings or at least cover several regions radially.As a result, it is possible to determine higher orders of the cornealsurface. However, in contrast to Placido topographs, a gap-freemeasurement of the corneal surface in conjunction with the OCTmeasurement is not {12072557.1} 9 expedient so as to enable thedetection of so-called Skrew rays. Therefore a keratometer with morethan 800 and less than 1600 measurement points is particularlypreferred. This provides a good application-oriented compromise betweentopography resolution and the detectability of Skrew rays.

The necessity for taking Skrew rays into account is explained below:

What the use of a keratometer with several separate measurement pointsinstead of a Placido topograph ensures is that even so-called Skrew raysare correctly taken into account when evaluating the local curvatures.This is particularly important because the local curvature of the corneais important for the refraction of the OCT measurement beam into thecornea and hence into the eye. Errors in the curvature, in particularthose which deflect the OCT beam out of the nominal meridian plane ofthe B-scan, lead to an erroneous positioning of the intraocularinterfaces appearing in the B-scan. What is particularly serious in thiscase is that although the angle error in the refraction may be small,the positioning error connected therewith increases with increasingintraocular distance.

This is illustrated in FIG. 4 . The left-hand side of FIG. 4 shows asurface element of the cornea, which is only tilted radially. The vectorarea 41 therefore does not have an azimuthal component. Hence the OCTbeam 42 which impinges on the corneal surface element as OCT beam 43 isalso only refracted in the meridional plane. The right-hand side shows asurface element 44, which is also tilted in the azimuthal direction.This tilt is not detected by a conventional Placido or ring-projectionsystem since the reflections out of the meridional plane superpose onreflections of other, neighboring corneal regions and the two componentscannot be readily separated. By contrast, a multi-point keratometer isable to detect this since the reflection point on a detector of thekeratometer appears outside of the meridional plane and—provided theillumination points are not situated very close together—no reflectionsfrom other illumination points interfere there. However, this tilt ofthe surface element now leads to an OCT beam 45, which falls onto thesurface element with vector area 44, likewise being refracted out of themeridional plane as OCT beam 46. Hence an intraocular interface in theA-scan will likewise not lie in the meridional plane, but to the sidethereof. Hence, without detecting this azimuthal tilt, the intraocularinterface will be reproduced erroneously for forming a model of the eye.

In order to obtain a better assignability of the detected keratometerpoints to the associated illumination sources, it is advantageous forthe keratometer in an additional embodiment if the keratometer pointsare sequentially illuminated and measured, either individually or ingroups. This is particularly advantageous in the case of 2 or moregroups of keratometer measurement points which in each case measure amajority of the corneal surface, and wherein the respective cornealareas overlap completely or to a large extent, but the keratometerpoints of the groups are in each case offset or rotated with respect toone another. As a result, for the measurement of one group, this ensuresthat the distance between two points of the group is large enough toachieve a reliable association between illumination source and detectedspot but that the cornea can nevertheless still be measured with a highresolution by measuring various groups of keratometer measurementpoints. Thus, for example, in the case of an 18 point keratometer, themeasurement can take place with 3 sub-groups, each with 6 points.

Furthermore, in an example embodiment as per FIG. 3 , at least one ormore B-scans 31 to 36 of the OCT pass through one or more of thekeratometer illumination points 37. This is particularly advantageous ifkeratometer data of the corneal surface should be combined withintraocular distances, obtained by OCT, to form a whole-eye model forthe IOL calculation by means of ray tracing. Aligning the B-scans at thekeratometer measurement points ensures that, when composing data of thecorneal front side from the keratometry and the intraocular data fromthe OCT, the OCT data are measured at the same position as thereflections from the corneal front side in the keratometer.

In so doing, the keratometer and OCT can be measured simultaneously withthe help of a dichroic separation—to this end, the beam splitter 3 inFIG. 1 has a dichroic design—or simultaneously by removing the OCTillumination spot detectable in the keratometer image by software oralternately/sequentially in time with a little time delay (i.e. under aslight shift due to the eye movement). Alternatively, each of the twomodalities can also be recorded separately, either simultaneously or inthe same time-window with an iris and/or pupil and/or sclera image andbe positioned laterally with respect to one another on the basis of saidimage. These types of separation of the OCT signal from the keratometersignal are not restricted to a keratometer but can also be applied to aPlacido topograph instead of a keratometer.

In a further example embodiment—likewise depicted in FIG. 3 —the B-scansof the OCT do not only pass through the keratometer points 37 but alsoform pairs, the scanning planes of which, e.g. 31 and 32, arerespectively perpendicular to one another, wherein the various pairs arerotated with respect to one another in order to cover as manykeratometer points as possible or all keratometer points.

An advantage of this is that, as per U.S. Pat. No. 7,452,077, a cornealvertex is determined for each pair and this vertex can be compared tothe vertex of the cornea, as determined from the keratometermeasurement. If the distance of the OCT vertex and the keratometervertex varies too strongly during a sequence of OCT and keratometermeasurements, this is an indication that the patient is not properlyfixed and that the assignment of the OCT scans to the keratometermeasurement points is not reliable enough for producing an eye modelfrom keratometer and OCT data.

The following text describes the OCT system, with which the multi-pointkeratometer is advantageously combined for the biometricmeasurement/detection of the whole eye.

In accordance with FIG. 1 , the OCT system consists of a swept-sourceinterferometer 13, a collimator 14, at least one laterally deflectingscanner 11 and/or 12 and several optical elements or lenses, 18, 19 and20, which serve to fix the focus plane of the OCT in the eye. Theswept-source interferometer itself is sketched in 2 variants in FIGS. 5a and b . Here, this is a Mach-Zehner arrangement in both cases, butother arrangements are also feasible.

As mentioned at the outset, swept-source systems are particularlysuitable for recording whole-eye OCT scans due to the high sensitivitythereof. In particular, it is advantageous to satisfy the conditions asdescribed in DE 10 2008 063 225 in the combination instrument. Here, anOCT wavelength of, for example, between 780 nm and 1100 nm, or inanother example between 1010 nm and 1090 nm should also be selected forthe application since light of these wavelengths is not perceived by thepatient eye and can still penetrate well through eye lenses made opaqueby the cataract. Within the scope of a combined instrument, a wavelengthof 680-980 nm or greater than 1100 nm lends itself to be selected forthe keratometer for the purposes of color separation.

Furthermore, the reliability of the obtained OCT signals can be improvedin a further embodiment if, in addition to the sample interferometer, areference interferometer is present for monitoring the laser wavelengthduring the sweep.

In this respect, FIG. 5A shows a specific design of a swept-source OCTsystem. Here, the light for the reference interferometer is decoupleddirectly after the light source or before the optical elements which arerequired for the actual sample measurement and sample referencing. Anadvantage of this is that the reference interferometer can be integratedinto a swept-source laser module. Alternatively, FIG. 5B shows anarrangement in which this reference interferometer does not lieimmediately in the light source itself or does not lie in front of theoptical elements which are required for the actual sample measurementand sample referencing, but rather lies thereafter.

In another example embodiment, a switch is undertaken between a retinamode and an anterior chamber mode by means of a delay line. In the caseof the retina mode, the focus of the OCT illumination beam and the zeropoint of the coherence gate are set in the vicinity of the retina. Thezero point of the coherence gate is in this case preferably set behindthe retina. Furthermore, the point of rotation during the B-scan lies inthe eye pupil such that, as in the case of a pure retina OCT, aB-scan/cross-sectional recording of the retina is brought about with ahigh lateral and axial resolution. In the case of the anterior chambermode, the focus of the OCT illumination beam and the zero point of thecoherence gate lie near or in the anterior chamber. It is particularlypreferable for the focus to lie in the anterior chamber and for the zeropoint of the coherence gate to lie in front of the cornea. Furthermore,the point of rotation lies—virtually—in the vicinity of the retina suchthat the B-scan supplies a high-resolution cross-sectional image of theanterior chamber, as is known from anterior chamber OCTs.

However, a high sensitivity of the swept-source OCT ensures in both scanmodes that the part of the eye that is not in focus is also available asa signal. This is shown in FIGS. 2 a and 2 b . In the anterior chambermode depicted in FIG. 2 a , the signal from the retina R is alsopresent, albeit not with a high lateral resolution. In the retina modedepicted in FIG. 2 b , the signal from the corneal front side CV is alsopresent. Hence, the A-scan, which in each case takes place along themain instrument axis—and which is the same as the visual axis of thepatient which is aligned by a fixing light —, can link the B-scans ofboth modes to one another axially and compensate for axial movements ofthe eye between 2 scans in different modes. In principle, the detectionof one common interface is sufficient, but it is often unclear in aninterface signal as to what interface this actually is. Here, in thevarious modes, 2 interface signals per scan supply a betterassignability to the interfaces in the eye.

In a further example embodiment, the delay line is extended in theanterior chamber mode compared to the retina mode by further opticalelements. This happens so that fewer optical elements of the measuringinstrument are in the beam path in the case of the retina mode such thatthe lower retina signal is not further attenuated by reflections atoptical elements of the instrument. By contrast, for the strongersignals from the anterior chamber—due to higher refractive index changesand fewer optical elements of the eye in the measurement beam pathcompared to signals from the retina—the attenuation of the signal byreflections at the focus-shifting and delay line-shifting optical unitscan be tolerated. An embodiment is described in FIG. 1 , in which theswitch to the anterior chamber mode is achieved by pivoting in the lens18, tipping away the lens 20 and inserting the prism 16.

In a further embodiment, the device has one or more LEDs forilluminating the eye and/or the close surroundings thereof. In FIG. 1 ,only LED 25 of these LEDs is shown in an exemplary manner. A recordingby the image sensor of the keratometer then supplies an image which isused for lateral positioning of the instrument in relation to the eye orfor determining the distance from limbus to limbus. In this case, it isadvantageous if, in contrast to the keratometer measurement, there is achange in the focus position for focusing on the surroundings of the eyeby pivoting lenses in and/or out. The lateral positioning of theinstrument by means of surrounding image can be complemented by axialpositioning using an OCT measurement in the anterior chamber mode.

In a further embodiment, the device has one or more LEDs forilluminating the sclera. In respect of the emitted wavelengths, theseare selected for good contrast of the blood vessels and/or the iris. InFIG. 1 , only LED 26 of these LEDs is shown in an exemplary manner. Arecording by the image sensor of the keratometer then supplies an imagewhich enables the lateral and rotational registration of the OCT and/ormulti-point keratometer measurement values in relation to the eye. Thisregistration can be used for forming an eye model from the measurementvalues or for the subsequent intraoperative alignment of an intraocularlens.

All elements and embodiments described in the explanations abovecontribute in their totality to increasing the speed, reliability,robustness and accuracy of the measurement of biometric variables, asare required for calculating intraocular lenses.

Not all aspects are necessarily used for a different measurement object.By way of example, if an instrument should only measure a cross sectionof the anterior chamber and the axis length of the eye, it is sufficientin a combined instrument of multi-point keratometer and anterior chamberOCT for only the anterior chamber to be detected by the OCT rather thanthe whole eye. Then the OCT need not cover the whole eye and it is thenadvantageously possible to combine other OCT systems, such astime-domain and spectrometer-based systems, with the multi-pointkeratometer. This is because all these OCT/multi-point keratometersystems profit from taking the Skrew rays into account for obtainingdata for the corneal surface, which then in turn are used for thelateral localization/assignment of the OCT data.

LIST OF REFERENCE SIGNS

-   -   1 Keratometer system    -   2 OCT system    -   3 Beam splitter    -   4 LED    -   5 Camera, area sensor    -   6 Telecentricity aperture    -   7, 8 Lenses for setting the foci    -   9 Objective lens    -   10 Beam splitter    -   11, 12 Pivotable mirrors    -   13 OCT interferometer    -   14 Collimator    -   15 Optical waveguide    -   16 Insertable prism    -   17 Beam deflection    -   18, 19, 20 Lenses for setting the foci and the field    -   21 Shutter    -   22 Beam splitter    -   23 Photodiode power measurement    -   24 Fixing LED    -   25 Surrounding illumination LED    -   26 Sclera illumination LED    -   27 Eye    -   28 Instrument axis    -   29 Attachment lens    -   30 Instrument axis    -   31-36 B-scan directions    -   37 Keratometer illumination measurement points    -   41, 44 Surface element vectors    -   42, 45 Incident OCT beam    -   43, 46 OCT beam optically refracted at the surface element    -   47 OCT scanning and corneal central plane    -   50 Swept-source source    -   51, 52, 53 Couplers    -   54 Reference interferometer    -   55, 56 Balanced detectors    -   58 Path length adaptation    -   59 Collimator at the interferometer    -   CV Corneal front side    -   R Retina

Various embodiments of systems, devices, and methods have been describedherein. These embodiments are given only by way of example and are notintended to limit the scope of the claimed inventions. It should beappreciated, moreover, that the various features of the embodiments thathave been described may be combined in various ways to produce numerousadditional embodiments. Moreover, while various materials, dimensions,shapes, configurations and locations, etc. have been described for usewith disclosed embodiments, others besides those disclosed may beutilized without exceeding the scope of the claimed inventions.

Persons of ordinary skill in the relevant arts will recognize that thesubject matter hereof may comprise fewer features than illustrated inany individual embodiment described above. The embodiments describedherein are not meant to be an exhaustive presentation of the ways inwhich the various features of the subject matter hereof may be combined.Accordingly, the embodiments are not mutually exclusive combinations offeatures; rather, the various embodiments can comprise a combination ofdifferent individual features selected from different individualembodiments, as understood by persons of ordinary skill in the art.Moreover, elements described with respect to one embodiment can beimplemented in other embodiments even when not described in suchembodiments unless otherwise noted.

Although a dependent claim may refer in the claims to a specificcombination with one or more other claims, other embodiments can alsoinclude a combination of the dependent claim with the subject matter ofeach other dependent claim or a combination of one or more features withother dependent or independent claims. Such combinations are proposedherein unless it is stated that a specific combination is not intended.

Any incorporation by reference of documents above is limited such thatno subject matter is incorporated that is contrary to the explicitdisclosure herein. Any incorporation by reference of documents above isfurther limited such that no claims included in the documents areincorporated by reference herein. Any incorporation by reference ofdocuments above is yet further limited such that any definitionsprovided in the documents are not incorporated by reference hereinunless expressly included herein.

For purposes of interpreting the claims, it is expressly intended thatthe provisions of 35 U.S.C. § 112(f) are not to be invoked unless thespecific terms “means for” or “step for” are recited in a claim.

1. (canceled)
 2. A device for measuring biometric variables of eyes,comprising: a multi-point keratometer and an OCT arrangement; themultipoint keratometer comprising an illumination structure; theillumination structure comprising illumination points; wherein theillumination points are arranged in several rings concentrically aroundan instrument axis; and wherein the several rings include a first ring,a second ring and a third ring and the illumination points on the firstring and the third ring are rotated in relation to the illuminationpoints on the second ring.
 3. The device as claimed in claim 2, whereinthe illumination points on the first ring and the third ring are locatedin a gap between the illumination points on the second ring.
 4. Thedevice as claimed in claim 2, wherein the illumination points on thefirst ring and the third ring are located offset thirty degrees ofrotation from the illumination points on the second ring.
 5. The deviceas claimed in claim 2, wherein the illumination points on the first ringand the third ring are located on radials that are thirty degrees,ninety degrees and one hundred fifty degrees from horizontal.
 6. Thedevice as claimed in claim 2, wherein the illumination points on thesecond ring are located on radials that are zero degrees, sixty degreesand one hundred twenty degrees from horizontal.
 7. The device as claimedin claim 2, wherein the illumination points on the first ring and thethird ring are located on radials that are thirty degrees, ninetydegrees and one hundred fifty degrees from horizontal and theillumination points on the second ring are located on radials that arezero degrees, sixty degrees and one hundred twenty degrees fromhorizontal.
 8. The device as claimed in claim 2, wherein theillumination points on each ring are arranged equidistantly about thering,
 9. The device as claimed in claim 2, wherein the illuminationpoints are arranged six on each ring.
 10. The device as claimed in claim2, wherein the illumination points are arranged in three ringsconcentrically around an instrument axis.
 11. The device as claimed inclaim 2, wherein the illumination points are arranged in several ringsat different radial distances from the instrument axis.
 12. The deviceas claimed in claim 2, wherein the illumination structure comprisesillumination points that lie in regions at which a Zernike descriptionof a corneal surface to be measured at a low order is expected to havelargest deviations compared to a spherical surface.
 13. A device formeasuring biometric variables of eyes, comprising: a multi-pointkeratometer and an OCT arrangement; the multipoint keratometercomprising an illumination structure; the illumination structurecomprising illumination points; wherein the illumination points arearranged in several rings concentrically around an instrument axis; andwherein the several rings include a first ring and a second ring;wherein the illumination points on the second ring are rotated inrelation to the illumination points on the first ring such that theillumination points on the second ring are located in gaps between theillumination points on the first ring.
 14. The device as claimed inclaim 13, wherein the several rings further include a third ring inwhich the illumination points of the third ring are rotated in relationto the illumination points of the second ring such that the illuminationpoints of the third ring are also located in the gaps between theillumination points of the second ring.